Is There a “diff” Tool for Images?

Yes, there is! In the realm of text files, the diff tool is a powerful utility that allows us to compare differences between two files. But when it comes to images, can we do the same? The answer is a resounding yes. There are several tools available that allow us to compare images, much like how diff works for text files. In this article, we’ll explore some of these tools and how to use them.

ImageMagick

ImageMagick is a robust collection of tools and libraries to read, write and manipulate an image in any of the more popular image formats. It includes a utility called compare which can be used to compare images either visually or using various metrics.

To install ImageMagick, use the following command:

sudo apt-get install imagemagick imagemagick-doc

Once installed, you can compare two images using the compare utility. Here’s an example:

compare -metric PSNR image1.png image2.png difference.png

In the above command, -metric is an option that sets the metric type to be used during comparison. PSNR stands for Peak Signal to Noise Ratio, a common metric used for image comparison. image1.png and image2.png are the images to be compared, and difference.png is the output image that will highlight the differences.

OpenImageIO

OpenImageIO is a library for reading and writing images, and a bunch of related classes, utilities, and applications. The openimageio-tools package includes a command called idiff that can be used to compare images.

To install OpenImageIO, use the following command:

sudo apt-get install openimageio-tools

Once installed, you can compare two images using the idiff command. Here’s an example:

idiff image1.png image2.png

In the above command, image1.png and image2.png are the images to be compared. The idiff command will output the differences between the two images.

PerceptualDiff

PerceptualDiff is an image comparison utility that makes use of a computational model of the human visual system to compare two images.

To install PerceptualDiff, use the following command:

sudo apt-get install perceptualdiff

Once installed, you can compare two images using the perceptualdiff command. Here’s an example:

perceptualdiff image1.png image2.png

In the above command, image1.png and image2.png are the images to be compared. The perceptualdiff command will output the perceptual differences between the two images.

Beyond Compare

Beyond Compare is a powerful time-saving utility for comparing files and folders. Although it’s not open-source, it does offer a visual comparison of images.

You can download Beyond Compare from their official website. Once installed, it integrates into the file explorer and provides a visual comparison of images.

Geeqie

Geeqie is a lightweight image viewer that can also find similar or duplicate images throughout a directory structure.

To install Geeqie, use the following command:

sudo apt-get install geeqie

Once installed, you can use Geeqie to compare images based on checksum, filename, or similarity levels.

Conclusion

Comparing images is not as straightforward as comparing text files, but with the right tools, it can be done effectively. The tools we’ve discussed in this article are powerful and flexible, each with their own strengths and capabilities. Whether you need to compare images for web development, graphic design, or just to find duplicates, there’s a tool out there that can help.